THE DIFFUSION-COEFFICIENT BEYOND TST AND JUMP THEORY

Jump theory (JT) and transition state theory (TST) are usually employe d to study atom diffusion at crystal surfaces. In the Fokker-Planck (F P) approach the continuous motion of the diffusing particle and the no n-equilibrium effects are incorporated in a natural way; JT and TST re sults are obtained as limiting cases in certain ranges of the paramete rs. High-temperature and low-friction effects are studied solving the FP equation with a periodic adiabatic potential and a position-depende nt friction.